Until now, display devices using an organic light emitting diode (OLED), a liquid crystal display (LCD), a vacuum fluorescent display, and a field emission display (FED) have been proposed as display panels for displaying images. Dots which are minimum light emitting units are two-dimensionally arranged in the flat display panels described above.
The luminance of each dot is controlled in the following manner so that the dots simultaneously emit light. As an example, the dots are controlled in sequential time series (dot drive) to display an image on the display panel. Further, as another example, dots belonging to a line obtained by arranging the dots on a straight line are controlled in time series for each line to simultaneously emit light (line drive), thereby displaying an image on the display panel. As still another example, all dots belonging to a frame constituting one screen are controlled for each frame to simultaneously emit light (frame drive), thereby displaying an image on the display panel.
In a case where light of one color is emitted, a black-and-white image is provided. In a case where three dots respectively corresponding to three primary colors of red (R), green (G) and blue (B) are defined as one group to emit light, a color image is provided. Various techniques for controlling the dots have been proposed. For example, in a display device using a VFD, there has been proposed a driving technique in which respective dots corresponding to divided grid series are scanned in the right or left direction during the same period, and a duty cycle thereof is increased multiple times (see Paragraphs [0033] to [0035] and FIG. 4 of Japanese Patent Application Publication No. 2000-306532).
Recently, as technologies for display devices are developed every year and images of higher precision and large screen are required, the number of dots has been rapidly increased. In connection therewith, there are unsolved problems in that driving circuits also needs to be developed every year to drive a larger number of dots.
As a result of an increase in the number of dots, in the conventional case, the time required to drive one dot is shortened, and the luminance of each dot (dot luminance) should be set high to obtain an image with high luminance. However, in a case where the dot luminance is set high, the lifespan of the various types of display panels described above is shortened. In a case where the line drive is employed, there is an additional problem in that the quality of images displayed is degraded due to interference between lines.
A display device using an OLED has recently come into the spotlight in terms of thin and light display devices. In a case where the luminance of dots in the OLED is increased, particularly as compared with other display panels, the lifespan of the display panel is shortened, and the interference between lines is increased.